1. Field of the Invention
The present invention relates to a linear rail bar, and more particularly, a linear rail bar whose two adjacent balls are separated by a spacer so as to prevent colliding and impacting each other thereby minimizing noise produced by the linear rail bar.
2. Description of the Prior Art
A well-known conventional linear rail bar is formed of a long infinitely extendable bar and a slider unit. The slider unit includes a slider body, two end caps for turning moving direction of rolling balls and other accessories. Both rail bar and the slider body are formed of grooves on their surface for a plurality of balls to roll therein, and a returning passage is provided in the slider body for recycling of the balls. This returning passage and the turning passage in the two end caps form a load free passage of the balls; while the grooves of both rail bar and slider body are combine to form a loaded passage of the balls. The load free passage and the loaded passage combine to construct a recycling passage which allows a predetermined amount of balls to make an infinitely recycling motion therein. With the aid of rolling balls, the slider is able to move along the rail bar less frictionally.
The track of the linear rail bar in the loaded passage is approximately a straight line, and change of moving direction of balls in the turning passage is quite large. The irregular change of moving speed of individual balls produced when they are passing along the track of varying curvature causes collision and impact between adjacent balls. Such collision and impact bring about particularly serious noise and vibration of the linear rail bar in the case those balls are made of metallic material. Besides, frictional contact between two adjacent balls moving in different direction may cause the above-mentioned noise and vibration more intensified. Although there have been developed some preferable materials, (for example, ceramic) which can be employed to fabricate balls with advantages of light weight, low impact energy, better hardness, anti-abrasion and better damping characteristic, yet they are considerably expensive which limits them to be usable only for linear rail bars in special application field and not widely applicable generally.
For solving the problem of mutual collision and impact of balls in the turning passage under the end caps, a method is suggested by U.S. Pat. No. 4,505,522 in which accommodative amount of balls is reduced in the turning passage so as to alleviate the change of amount of balls thereof. Meanwhile, in order to realized such an object, the geometrical figure of the turning passage has to be formed so precisely that resulting in complicating fabrication of a linear rail bar.
A remedy for improving mutual collision and impact of balls in the loaded passage of a linear rail bar is shown in FIG. 7. As shown in FIG. 7, a plurality of balls 4 are rolling in grooves 11 of a rail bar and grooves 21 of a slider body. A smaller spacer ball 6 is interposed between two adjacent balls 4, the rotating direction of the spacer ball 6 is in reverse that of the two adjacent balls 4 so that rotation at the contact surface of two balls 4 and 6 is the same thereby reducing frictional resistance between the balls 4 and improving mobility of the linear rail bar. Generally, the ball 4 and the spacer ball 6 are made of the same material. Although, by such means the exacerbated frictional resistance arising from the contact surface due to two adjacent balls 4 rotating in different direction in the loaded passage can be eliminated, yet there still remains no answer to the problem as to mutual collision and impact of balls 4 moving along in the turning passage due to change of speed.
The U.S. Pat. No. 5,615,955 suggested use of oil immersed plastic spacer balls 6 in those shown in FIG. 7 to exhibit both anti-vibration property of plastic material and lubrication effect. Such a system improves better flexibility due to deformation and reduces noise of impact, however, the advantages above are counteracted by the lowering of mechanical strength of the linear rail bar because due to the occupation of room in the loaded passage by the spacers 6 whose sizes nearly equal that of the ball 4, thus reducing the amount of ball 4 to accommodate the loaded passage to almost half of original value.
The present invention has been made in order to eliminate the inconvenience inherent to the conventional techniques as mentioned above. One object of the present invention is to provide a linear rail bar having a spacer between two adjacent balls for reducing noise and vibration arising from mutual collision and impact between adjacent balls.
It is another object of the present invention to provide a linear rail bar having a spacer between two adjacent balls, and the spacer is made as small as possible not to occupy two much spacing to make room for more balls in a loaded passage so as to enhance strength of the linear rail bar.
It is still another object of the present invention to provide a linear rail bar having a spacer made of oil containing plastic material and provided with lubricant path so as to lower the friction of the linear rail bar.
In keeping with an aspect of the present invention, this and other objects mentioned above are accomplished by providing an anti-noise and anti-vibration spacer between adjacent balls, formed in a cylindrical shape with both end surfaces thereof formed into an inwardly concaved surface so as to match the shape of the ball thereby greatly reducing the space required for the spacer that in turn increasing accommodative amount of balls in the loaded passage and enhancing the mechanical strength of the present invention.
In the present invention, for preventing the unrolling cylindrical spacer from increasing contact friction between the passage walls, the outer diameter of the cylinder is made smaller than that of the ball.
In the present invention, for preventing the spacer from contacting the side wall surfaces of abruptly curved turning passage, and even producing a normal pressure to the wall surfaces so as to exacerbate the increase of frictional resistance, the spacer is divided into two butt jointed truncated cone shaped bodies with the diameter at the middle portion thereof smaller than that at the two ends so as to make contact surface with the passage as less as possible.
For preventing earlier breakage of an oil film on the ball surface, the contact area between the ball and the spacer shall be kept as small as possible. The inward concavity at the end surface of the spacer is formed of two conical arcuate surfaces as it is observed from the front, and the radius thereof is slightly larger than that of the ball so that the contact surface between the ball and the spacer can be minimized as small as approaching to a point.
In the present invention, for improving lubricating effect of the spacer, a let through hole is provide therein so as to accept the lubricant oil exuded from the oil film on the ball in contact and impart this oil to the next ball thereby accomplishing lubrication effect and cooling effect as well.
In the present invention, for eliminating the disadvantage that the lubricating oil can not pass smoothly through the closed contact surface between the ball and the spacer, and instead, passing via the let through hole, the inwardly concaved surface of the spacer is formed into a sinuate shape so as to divide the contact surface between the ball and the spacer into a plurality of intermittent contact points thereby improving the flow of lubricating oil and lowering frictional resistance as well.
In the present invention, materials for example, plastics, high molecular compounds, reinforced plastics, and ceramic are usable for fabricating low friction and anti-abrasive spacer.
Besides, oil containing materials are recommendable for fabricating the spacer so as to save consuming lubrication oil in a linear rail bar.